Of the survey participants who labeled themselves as middle class, 50 percent earn between $50,000 and $125,000 annually. The actual dollar amounts needed to qualify as middle class are slightly lower. Pew Research Center defines it as adults whose annual household income is two-thirds to double the national median, which was $55,775 as of 2016.

That means singles making between $24,000 and $72,000 annually are middle class by 2016 standards. The median household income in the U.S. recently rose to $59,039, so the new parameters are slightly higher when adjusted for household size.

A few common mindsets also bind together those who consider themselves middle class, Northwestern Mutual found. In general, people in the middle class are:

More likely to believe in the attainability of the American Dream. While 55 percent of middle-class survey respondents say they believe in the American Dream, only 48 percent of the general population say they do.

More likely to have a clear and accurate picture of their finances. While 71 percent of middle-class respondents feel as though they have a clear picture of their finances, only 64 percent of the general population say they do.

More likely to feel very financially secure. While 58 percent middle-class survey respondents say they feel financially secure, only 47 percent of the general population say the same.